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SqlCommand.ExecuteScalar Method

Executes the query, and returns the first column of the first row in the result set returned by the query. Additional columns or rows are ignored.

Namespace:  System.Data.SqlClient
Assembly:  System.Data (in System.Data.dll)

'Declaration
Public Overrides Function ExecuteScalar As Object

Return Value

Type: System.Object
The first column of the first row in the result set, or a null reference (Nothing in Visual Basic) if the result set is empty. Returns a maximum of 2033 characters.

Implements

IDbCommand.ExecuteScalar

ExceptionCondition
InvalidCastException

A SqlDbType other than Binary or VarBinary was used when Value was set to Stream. For more information about streaming, see SqlClient Streaming Support.

A SqlDbType other than Char, NChar, NVarChar, VarChar, or Xml was used when Value was set to TextReader.

A SqlDbType other than Xml was used when Value was set to XmlReader.

SqlException

An exception occurred while executing the command against a locked row. This exception is not generated when you are using Microsoft .NET Framework version 1.0.

A timeout occurred during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

InvalidOperationException

The SqlConnection closed or dropped during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

IOException

An error occurred in a Stream, XmlReader or TextReader object during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

ObjectDisposedException

The Stream, XmlReader or TextReader object was closed during a streaming operation. For more information about streaming, see SqlClient Streaming Support.

Use the ExecuteScalar method to retrieve a single value (for example, an aggregate value) from a database. This requires less code than using the ExecuteReader method, and then performing the operations that you need to generate the single value using the data returned by a SqlDataReader.

A typical ExecuteScalar query can be formatted as in the following C# example:

 cmd.CommandText = "SELECT COUNT(*) FROM dbo.region";
 Int32 count = (Int32) cmd.ExecuteScalar();

The following example creates a SqlCommand and then executes it using ExecuteScalar. The example is passed a string representing a new value to be inserted into a table, and a string to use to connect to the data source. The function returns the new Identity column value if a new row was inserted, 0 on failure.

Public Function AddProductCategory( _
  ByVal newName As String, ByVal connString As String) As Integer 
    Dim newProdID As Int32 = 0
    Dim sql As String = _
     "INSERT INTO Production.ProductCategory (Name) VALUES (@Name); " _
       & "SELECT CAST(scope_identity() AS int);" 

    Using conn As New SqlConnection(connString)
        Dim cmd As New SqlCommand(sql, conn)
        cmd.Parameters.Add("@Name", SqlDbType.VarChar)
        cmd.Parameters("@Name").Value = newName
        Try
            conn.Open()
            newProdID = Convert.ToInt32(cmd.ExecuteScalar())
        Catch ex As Exception
            Console.WriteLine(ex.Message)
        End Try 
    End Using 

    Return newProdID
End Function

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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